1. Field of the Invention
The present invention relates to an apparatus for designating an area for image processing.
2. Related Background Art
A conventional image processing system such as a copying machine has a trimming function for extracting an arbitrary area of an original and a function for designating two diagonal points (P.sub.1,P.sub.2) of a rectangular and/or square area (FIG. 2-1) by using a digitizer as an area designating means (the latter scheme is called an opposite angle scheme hereinafter) in order to realize a masking function or the like (U.S. Ser. No. 884,677).
When an area such as a combination of a square and/or a rectangular areas is to be designated according to this opposite angle scheme, the area is divided into the squares and/or rectangles and must be designated by two pairs of diagonal points (P.sub.3,P.sub.4) and (P.sub.5,P.sub.6). In this case, it is difficult for an operator to divide a complicated area into a plurality of rectangles and/or squares. In addition, it is also difficult to ideally designate the divided portions without gaps, thus degrading operability. In order to improve operability, a scheme is proposed to input points in an order of P.sub.7, P.sub.8, P.sub.9, P.sub.10, P.sub.11, P.sub.12, and P.sub.7 so as to surround the area to be designated with numeric keys (FIG. 2-3) as described in U.S. Ser. No. 942,035. According to this scheme, an area having a complicated area can be easily designated (this scheme is called a corner scheme hereinafter). According to the corner scheme, however, five (i.e., P.sub.13, P.sub.14, P.sub.15, P.sub.16, and P.sub.13) or four points must be designated for even a simple area (FIG. 2-4), as described in U.S. Ser. No. 756,338, thus degrading operability.
A scheme for inputting area coordinates with a ten-key pad as an area designating means described in U.S. Ser. No. 4,517,606 requires reading of coordinates by a scale or the like and a large number of key strokes. In order to solve this problem, a two-dimensional coordinate input apparatus such as a digitizer described in U.S. Ser. No. 884,677 is available.
In the two-dimensional coordinate input apparatus such as a digitizer, a desired area on the original can be directly designated, thus greatly improving operability. According to this apparatus, however, flexibility of area designation is often beyond the capability of hardware. For example, an area having a shape which cannot be trimmed due to hardware limitations is undesirably designated.